Can Subclinical Rickets Cause SCFE? A Prospective, Pilot Study.

BACKGROUND: Slipped capital femoral epiphysis (SCFE) is a common disorder of the growing hip; however, its etiology remains unknown. Vitamin D (25-OH) is a major regulator of bone homeostasis and calcium metabolism. Vitamin D deficiency is one of the major causes of rickets, and rickets has been associated with SCFE. Increased body mass index (BMI) has been linked to SCFE and obese children are known to have lower vitamin D levels. Therefore, we hypothesize that children who develop SCFE may have subclinical rickets predisposing them to the development of physeal disease.

METHODS: This was a pilot, prospective study designed to determine the relationship between vitamin D, bone, muscle, and fat in patients with SCFE. We enrolled 20 consecutive patients with idiopathic SCFE aged 9 to 14 years. Upon diagnosis, vitamin D, PTH, T4, and thyroid-stimulating hormone blood levels were obtained. A single-slice computed tomography was used to measure cortical bone density (CBD) of the femur. Demographics, BMI, and the results obtained were compared to generate a relationship between vitamin D levels and SCFE.

RESULTS: Twenty patients were enrolled, 13 males and 7 females, at an average age of 12 years (range, 9 to 14 y), and mean BMI% was 93.9 (range, 81.3 to 99.5). There were 15 stable and 5 unstable SCFE. Overall, mean and SD values for vitamin D, 25-OH were within the normal range (43.9 ± 13.5). We found no difference in values in vitamin D between nonobese (BMI < 95%) and obese (BMI ≥ 95%) subjects (34.8 ± 16.8 vs. 51.6 ± 22.4, P = 0.144). Moreover, we found no difference in CBD between these 2 groups (1126 ± 33.1 vs. 1147 ± 41.2, P = 0.333). There was no relation between blood values of vitamin D and measures of CBD.

CONCLUSIONS: Although obese children are known to have lower levels of vitamin D and a higher prevalence of SCFE, we found no correlation between low vitamin D and the development of SCFE in this subset of patients.